os/exec: exec.LookPath return errors when PATH starts with semicolon (parsed as contains empty string at first) and working directory is same as the target executable on windows

[ray1422]

Go version

go version go1.20.14 windows/amd64

Output of go env in your module/workspace:

set GO111MODULE=
set GOARCH=amd64
set GOBIN=
set GOCACHE=C:\Users\Administrator\AppData\Local\go-build
set GOENV=C:\Users\Administrator\AppData\Roaming\go\env
set GOEXE=.exe
set GOEXPERIMENT=
set GOFLAGS=
set GOHOSTARCH=amd64
set GOHOSTOS=windows
set GOINSECURE=
set GOMODCACHE=C:\Users\Administrator\go\pkg\mod
set GONOPROXY=
set GONOSUMDB=
set GOOS=windows
set GOPATH=C:\Users\Administrator\go
set GOPRIVATE=
set GOPROXY=https://proxy.golang.org,direct
set GOROOT=C:\Program Files\Go
set GOSUMDB=sum.golang.org
set GOTMPDIR=
set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64
set GOVCS=
set GOVERSION=go1.20.14
set GCCGO=gccgo
set GOAMD64=v1
set AR=ar
set CC=gcc
set CXX=g++
set CGO_ENABLED=1
set GOMOD=NUL
set GOWORK=
set CGO_CFLAGS=-O2 -g
set CGO_CPPFLAGS=
set CGO_CXXFLAGS=-O2 -g
set CGO_FFLAGS=-O2 -g
set CGO_LDFLAGS=-O2 -g
set PKG_CONFIG=pkg-config
set GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=C:\Users\Administrator\AppData\Local\Temp\go-build3123780178=/tmp/go-build -gno-record-gcc-switches

What did you do?

I have a file my.bat in C:\, and my program

package main

import (
	"fmt"
	"os"
	"os/exec"
)

func main() {
	os.Setenv("path", `;C:\`)
	s, err := exec.LookPath("my.bat")
	fmt.Printf("%s %v\n", s, err)
}

What did you see happen?

when this program executed with working dir C:\, it prints

my.bat exec: "my.bat": cannot run executable found relative to current directory

but when I execute it with other working dir, it parsed normally and printed

C:\my.bat <nil>

I think it's caused by dotErr is returned too early, although the executable do exist in the PATH.

What did you expect to see?

C:\ is in the path, it should print

C:\my.bat <nil>

no matter what working directory is it.

[gabyhelp]

Related Issues and Documentation

• os/exec: unexpected ErrDot returned if there is an empty path in PATH #61493 (closed)
• os/exec: Cmd.Dir is not checked when looking for executable on Windows #21675 (closed)
• os: StartProcess doesn't allow paths starting with "./" #58743 (closed)
• os/exec: document that LookPath result may only be valid relative to current directory #3622 (closed)
• proposal: os/exec: make LookPath not look in dot implicitly on Windows #38736 (closed)
• os/exec: Cmd does not attempt to run ./prog.exe, when execution of ./prog requested #7377 (closed)
• os/exec: PATH in windows ErrNotFound is not escaped #38994 (closed)
• os/exec: windows LookPath is broken #6224 (closed)
• os/exec: calling Cmd.Start after setting Cmd.Path manually to absolute path without ".exe" no longer implicitly adds ".exe" in Go 1.22 #66586 (closed)
• os/exec: return error when PATH lookup would use current directory #43724 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[seankhliao]

from the package docs:

To avoid those security problems, as of Go 1.19, this package will not resolve a program using an implicit or explicit path entry relative to the current directory. That is, if you run LookPath("go"), it will not successfully return ./go on Unix nor .\go.exe on Windows, no matter how the path is configured. Instead, if the usual path algorithms would result in that answer, these functions return an error err satisfying errors.Is(err, ErrDot).

closing as working as intended.

[ray1422]

It returns normally when removing the leading semicolon of the PATH.

If this is intended, all binary that registered as Windows services, with PWD C:\Windows\sys32, will be unable to call some commands.